The present invention relates to a testing device for a sewing machine capable of forming a succession of stitches or a stitch pattern on a work fabric through relative movements between the needle and work holding means under control of a batch of stitch position data.
In the art of electronically-controlled sewing machines for industrial applications wherein a stitch pattern is formed on the workpiece according to a batch of stitch position data stored in a memory provided in a drive control circuit, it is a common practice that a test run of the machine is conducted prior to starting a sewing operation in order to check if the stitch position data has been programmed without an error and correctly stored in the memory, and check if an intended stitch pattern is exactly formed at a predetermined position on the workpiece retained in a work holder. In such test run, only the work holder is moved according to the programmed data from one stitch position to another with intermittent actions stopping at each stitch position between the sewing start and end points while the needle is kept at rest, whereby the work holder is checked for necessary feed motions thereof to obtain the desired stitch pattern. Such a program testing practice is disclosed in British Patent Application filed in the name of the assignee of the present application, laid open Mar. 31, 1982 under Publication No. GB 2,083,846B.
In such manner of testing operation, however, a lot of time is required to trace a programmed stitch pattern with the intermittent movements of the work holder between adjacent stitches starting at the sewing start position, and consequently the testing operation is time-consuming and less efficient when it is sufficient to check the movements only at selected stitch positions, particularly where the programmed stitch pattern consists of a multiplicity of stitches.